The incursion of unwanted air and/or moisture into buildings and homes around door and window joints is a major concern for builders, property owners, and occupants. The penetration of air and/or moisture is a serious concern, and may result in exterior and interior damage if not prevented or corrected in a timely manner. In addition, heat losses caused by air leakage around building openings have taken on new significance due to today's high energy costs. Sealing such openings has typically been accomplished by caulking or using putty-like compound around openings between door and window frames to seal the gaps and prevent inward seepage of air and/or water into a building.
An existing approach to sealing window joints is the use of a sill pan to flash windows into a window opening. The sill pan is typically made of metal and is formed in an off-site fabrication shop based on measurements made of the opening at the building site. Typically there are variations in the size for each window so each pan is somewhat unique. Furthermore, if the measurement is not precise, the pan will not fit correctly, and must be remade or swapped around to make sure the sill pans fit each opening. An additional problem with metal sill pans is that sill pans create a thermal short from outside to inside of the window to be sealed due to the pans large mass, and creates condensation on the inside of the window at the sill.
A recent more common practice is the use of polyvinyl chloride (PVC) for sealing panels for windows. The PVC is made in two pieces that slide so they can be used in residential applications, which have become more common. The PVC based sill pans slide to fit the opening and are then sealed with glue or sealant to make a watertight assembly. The PVC based products can have built-in shims and other elements to create a slope for directing water drainage. The PVC material is usually thicker than metal. However, plasticized PVC can also have compatibility problems with bitumen based membranes. Furthermore, the PVC based sill product has openings at the point of connection of the two pieces that can be prone to leakage. Both the aluminum and plastic sill pans need to be bonded to the underlying surface so no water can pass underneath, which is typically achieved with non-skinning butyl beads or tapes.
A further trend has been the increased use of vinyl windows in recent years. However, it has been generally been recognized that vinyl windows take in water and can leak at the sills notwithstanding the weep holes built into the frame at the sill. Therefore, the use of vinyl windows has significantly increased the use of sill pans, not just flashing membranes. Many manufacturers now encourage the use of sill pans. An available option is to create a pan from a self-adhered membrane cutting it to fit. A self-adhered membrane that is cut to fit has the advantage of sealing to the underside of the window and forming the product in the field that it is not rigid. The self-adhered membrane will not allow drainage since the window will create a seal unless shims are put under the window to create sufficient space to create drainage. Many manufacturers of vinyl windows want the window to be fully supported which means shims do not work with their vinyl window designs. Furthermore, the membrane is not very durable and the cutting of the membrane can create joints and pinholes that must be filled with sealant to make sure a seal is created.
While many materials and approaches for sealing window and door joints have been tried, there still exists a need for a material and method of application that can be used for a sill pan that has the advantages of a self-adhered membrane, but can drain without shims, and has sufficient sealing materials to seal around nail holes, while being thin enough to properly function and provide end and back dams without cutting the material.